Model and marathoner Christy Turlington Burns was a major part of today's announcement about the release of the Apple Watch, revealed as the first person to use the device for fitness tracking outside of Apple's Cupertino, California, headquarters.

The video below, which Apple provided to Runner's World, shows Turlington Burns participating in the Kilimanjaro Half Marathon with the Apple Watch as she raises awareness for Every Mother Counts[1]—the nonprofit organization she founded with a focus on maternal health worldwide. Turlington Burns also will be blogging for Apple.com as she documents her training with the watch as she preps for the London Marathon[2] in April.

“I relied on it quite heavily [during the half marathon]," Turlington Burns told Apple CEO Tim Cook during the presentation. "The race was very challenging. There was a lot of altitude and elevation, so I was checking it quite frequently.”

London won't be Turlington Burns' first foray with 26.2 miles. She completed the New York City Marathon in 2011 (4:20) and 2013 (4:35), as well as the 2014 Chicago Marathon (4:04).[brightcove_autoplayoff_adsoff:4100817723001]